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PATENTBD FEB. I 23, 190,4,

P. GERMAIN.

MICROPHONE.

APPLIGATION'HLED 0015.7, 1899.

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UNITED STATES Patented February 23, 1904..

PIERRE GERMAIN, OF FONTENAY AUX ROSES, FRANCE.

MICROPHONE.

SPECIFICATION forming partof Letters Patent No. 753,062, dated February 23, 1904.

Application filed October 7, 1899.

T0 all whom it may concern:

Be it known that I, PIERRE GERMAIN, inspector of telegraphs, of Fontenay aux Roses, Department oi' Seine, France, have invented certain' new and useful Improvements in the Construction of Microphones, which improvements enable telephonie transmission to be effected under special conditions as regards intensity, allowing thereby reception -in loud tones by a magnetic receiver of the ordinary type, of which the following is a specification.

This invention relates to an improved microphone, and has for its object to provide means for improving the transmission.

In the sectional view in the accompanying drawing, c' is the mouth-piece, tting the chamloer 7e, which contains the microphone, composed of two carbon disks a and with the.

conducting medium d between them. The disk a is secured to the diaphragm f by a screw e, which diaphragm serves to seal the chamber from the outer air. Wires g g lead to and away from the microphone and convey the electric current for transmission, while the wires c c lead to a heating-coil w, surrounding the microphone. A casing y, perforated with holes s and containing potassium, sodium, or some other substance a', adapted to absorb the moisture and oxygen from the air, is secured to the wall of the chamber.

To improve the conductivity and clearness of transmission of the medium CZ, I incorporate with the carbon granules a metal or metallic oxid-for instance, oxid of silver one part to three parts of carbon. This may be directly incorporated with the ordinary carbon granules or may be incorporated with carbon mass before baking and baked in the form of sticks and afterward broken up to form the granules. this low-conductivity granule is not of this invention, an important part of which is to have a low conductivity in the microphone to permit the travel of large currents therethrough. HeatI have found to be of material aid in improving the transmission, and I may apply it in any manner. In the vdrawing I have shown it applied by a coil of wire w, connected to al source of electricity. This heating means should be capable of heating The manner of securing Serial No. 732,941. (No model.)

the conducting medium to about 80O centigrade. It is obvious that with so much heat in' the chambeix there would be liability to combustion of the particles. To prevent this, I place within the chamber-a quantity of poltassiuln'or sodium, (in this case we will assume itis sodium,) which has an aiiinity for oxygen and whose base, formed by the oxidation of the metal, has an affinity for water-vapors and carbonio acid. The granulate chamber being closed, the oxygen, water-vapor, and carbonio acid confined therein are absorbed by the sodium, and there remains only the nitrogen of the air, which cannot support combustion, and the carbonio oxid and the oxid of the metal forming the granulats, as well as the semiconductive divisions in the diaphragme between which the granulate is placed. Under these conditions perfect transmission can be obtainediK This method of obtaining an inert atmosphere is much superior to that which consists in exhausting the chamber containing the granulate by means of an air-pump, for then the chamber must be formed of rigid heavy walls unsuitable for microphonic sensitiveness. When exhausted by means of a pump and the rarefaction is complete, should a leak arise nothing can prevent the inrpsh of oxygen on account of atmospheric pressure, whereas whe-nan inert atmosphere has been chemically produced, as hereinbefore explained, an entry of fresh air is of no importance, for the sodium (with its affinity for oxygen) absorbs it as it penetrates; but with an inert atmosphere the penetration of air into the granulate-chamber would be very slow on account of the pressure in the microphonic chamber being the same as that oi' the atmosphere.

Having an inert atmosphere, no' matter what heating-currents are employed no oxidation of the metal of combustion of the carbon takes place, and a greatly-improved transmission is secured.

I claim as my inventionl. A microphonic transmitter having a chamber and chemical means inside said chamber to eliminate the oxygen contained therein, asand vfor the purpose described.

2. A microphonic transmitter having a IOO ehamberto contain the elements and sodium applying heat to the granulate, and means in said chamber, as and for the purpose set Within said chamber to eliminate the oxygen forth. contained therein.

3. A mierophonic transmitter having a In testimony WhereofIhave signedmy name I5 5 Chamber containing means for eliminating the to this specification in the presence of two subeombustion-supportirlig elemelilit of the air and seriloing Witnesses. means for app ying eat to t e chamber.

4. A mierophonie transmitter having a PIERRE GERMAIN chamber and granulate therein, composed of Witnesses: IO a mixture of carbon and some metal of good GUs'rAVE DUMONT,

conductivity, in combination with means for J. ALLIsoN BOWEN. 

